This invention is directed to a method and apparatus for inflating a safety device, such as a safety bag adapted for use in a transport vehicle. More specifically, this invention is directed to an improved miniaturized system adapted for use in locations where space is limited, such as in a steering wheel column of an automobile and employing a mixture of a stored compressed gas and a generated gas. Still more specifically, this invention is directed to a simplified method and apparatus in which the gas generating chamber is separate from, outside of and partially contiguous with the stored gas chamber.
The prior art reveals various methods and apparatus for using inflatable gas bags as a safety device to be employed in motor vehicles for the purpose of restraining passengers during impact in order to prevent serious injuries. Such gas inflatable safety bags have been proposed either as an alternative or as adjunct to seat belts which are employed in automobiles.
Although seat belts provide protection against serious injuries during automobile impact, seat belts are often not used. In order to overcome this failure to use seat belts and to provide protection to the motor vehicle driver and/or passengers without requiring any voluntary act on their part, the automobile industry has been developing gas inflated safety bags. One or more gas inflated safety bags are stored in the automobile and are actuated upon impact automatically. Such actuation causes the safety bag to be inflated with a gas instantaneously. Inflation of the safety bag restrains the automobile occupants in their seats during the critical moments following impact and helps to prevent serious injury.
The safety bags are inflated by means of a generated gas or a mixture of stored and generated gases which are under pressure and which are expanding in volume. Since the volume, according to Charles' Law, and the pressure, according to Gay-Lussac's Law, of an ideal gas vary directly with the absolute temperature of the gas, it is desirable to conserve the heat developed during generation of the gas so that such heat can be directed toward raising the temperature of the gas rather than being dissipated throughout the system and wasted. While there are other considerations regarding the heat developed by the generated gas, viewed from the standpoint of efficient use of gas volume and pressure, the less heat that is diffused and wasted throughout the system, the better, particularly where a miniaturized inflator is needed.
In some prior art designs, the gas used to inflate the safety bag is commonly a hybrid gas which results from mixing a stored gas from a pressurized container and a generated gas resulting from combustion of a pyrotechnic material in a gas generating chamber which is commonly disposed within the stored gas container. Location of the gas generating chamber within the stored gas chamber results in some amount of heat being transferred to and dissipated in the stored gas chamber and its outer casing. In other prior art designs, the generated gas or the hybrid gas passes through the stored gas chamber on its way to the safety bag, resulting in a transfer of heat to the casing of the stored gas chamber.
Many of the inflator devices known in the prior art are relatively large in size which prevents them from being installed in small locations, such as in the steering column adjacent to the steering wheel in an automobile and, instead, requires that they be located under the hood in the engine compartment of the automobile.
In some prior art designs, the stored gas chamber or the reservoir of pressurized gas and/or the gas generating chamber are physically remote from the inflatable safety bag, necessitating a series of conduits to connect the stored gas chamber and the gas generating chamber to the safety bag. What is needed is an improved design of inflator which allows the inflator to be sufficiently miniaturized in size so that the inflator can be located adjacent to the safety bag, thereby eliminating such conduits. Since the safety bag must, in turn, be located adjacent to the occupants of the vehicle, either driver or passenger, or both, this means that the inflator must be sufficiently miniaturized in size to be located in the passenger compartment of the automobile or adjacent to the passenger compartment of the automobile.
In some prior art designs, the combustion by-products and residue of the pyrotechnic material are allowed to pass into the stored gas chamber after combustion of the pyrotechnic material. This is undesirable because it contaminates the stored gas chamber with such combustion residue and may also contaminate the hybrid gas flowing into the safety bag.
U.S. Pat. 3,674,059 to Stephenson discloses apparatus for inflating a safety bag in which the gas generating chamber is physically positioned within the stored gas chamber.
U.S. Patent 3,663,036 to Johnson discloses a design in which some or all of the hot gas from the gas generating chamber is deflected through the stored gas chamber on its way to the safety bag.
U.S. Patent 3,642,304 to Johnson discloses a design in which the stored gas chamber and the gas generating chamber are connected to the safety bag by a series of conduits.
Other prior art of interest include U.S. Patents 3,655,217 to Johnson and 3,122,181 to Hebenstreit.